Quiz:Linear representation theory of symmetric group:S3

For background, see linear representation theory of symmetric group:S3.

View summary:

Item	Value
Degrees of irreducible representations over a splitting field (and in particular over $\mathbb{C}$)	1,1,2 maximum: 2, lcm: 2, number: 3 sum of squares: 6, quasirandom degree: 1
Schur index values of irreducible representations	1,1,1
Smallest ring of realization for all irreducible representations (characteristic zero)	$\mathbb{Z}$
Minimal splitting field, i.e., smallest field of realization for all irreducible representations (characteristic zero)	$\mathbb{Q}$ (hence, it is a rational representation group)
Condition for being a splitting field for this group	Any field of characteristic not two or three is a splitting field. In particular, $\mathbb{Q}$ and $\mathbb{R}$ are splitting fields.
Minimal splitting field in characteristic $p\ne 0,2,3$	The prime field ${\mathbb{F}}_p$
Smallest size splitting field	field:F5, i.e., the field of five elements.

Basic stuff

Up to equivalence, there are three irreducible representations of symmetric group:S3 in characteristic zero: the one-dimensional trivial representation, the one-dimensional sign representation (that sends every permutation to its sign), and the standard representation of symmetric group:S3, a two-dimensional representation.

1 Which of the irreducible representations is realized over the field of rational numbers?

	trivial representation only
	trivial representation and sign representation only
	all three representations

2 Which of the irreducible representations can be realized using orthogonal matrices (i.e., matrices in the orthogonal group for standard dot product) over the field of rational numbers?

	trivial representation only
	trivial representation and sign representation only
	all three representations

3 The symmetric group of degree three can also be viewed as a dihedral group of degree three and order six, acting on a set of size three. The 3-cycles become rotations and the transpositions become reflections. This defines a two-dimensional representation over the real numbers. Which of these is the two-dimensional representation?

	the standard representation
	the sum of the trivial and the sign representation
	the sum of two copies of the sign representation
	the sum of two copies of the trivial representation